The objectives of the proposed work are to obtain and make use of suitable mutations to analyze control of developmental patterns and maintenance of cell surface pattern in the ciliate Tetrahymena thermophila. These include the following approaches: (1) Continued selection of high- and low-temperature sensitive mutations affecting cell division, cell shape, and cell-surface pattern; this will include efforts to improve the efficiency of the selection procedures themselves. (2) Continued analysis of a mutation, janus, that brings about a large-scale reversal in organization of cortical fields; this will include an effort to superimpose a reversal of small-scale pattern (ciliary meridian rotation) on the large-scale field reversal. (3) Genetic and phenotypic analysis of three mutations, pseudomacrostome, that bring about a radical switch in developmental pathways; this will include an analysis of time of expression in the cell cycle and subjection to physiological perturbations that are known to influence pathway selection and oral organelle positioning in at least one of these mutants. (4) Comparative studies on cell surface organization, including the relationship of ciliary patterns to underlying mitochondrial asymmetries, in normal cells with and without ciliary meridian inversions and in disorganized mutant cells with irregular organization of ciliary meridians. (5) Attempts to obtain and analyze mutations affected in specific stages of a developmental transformation to a "rapid swimmer" phenotype.